The present invention relates to a projection type image display system, projector, program, information storage medium and image processing method which can execute a calibration in consideration of the influence of ambient light as well as the plane of projection.
When an image is to be projected through a projection type image display system such as projector, the image appearance may be varied under influence of the ambient light such as illuminating or external light and/or under influence of the plane of projection such as screen or wall. In order to reproduce an ideal image appearance by correcting the varied image appearance, an image display system has been proposed which is designed to automatically correct the image information based on measurements of calibration images and to project an image based on the corrected image information.
For example, Japanese Patent Laid-Open Application No. 2000-82137 discloses an image display system which corrects and displays an image by selecting and reading a desired brightness regulating value from a plurality of previously stored brightness regulating values, based on the value of illuminance. Such a system was generally used in the conventional art for correcting the image by selecting and reading a regulating value depending on the measured illuminance.
When the illuminance is used, however, the image display device can correct the brightness of the image, but not the color in the image.
When an image is displayed on a monitor or the like, the image display device can relatively simply and easily determine the regulating value based on only the illuminance because the material of the image display area is always invariable in property. When an image is projected onto a screen or the like, the image appearance will be varied depending on the color and property of the screen material in addition to the illuminance because the color (spectral reflectance) and property of the screen material are variable.
Even though the conventional system for selecting and applying the regulating values is taken, the image display device cannot properly regulate the image appearance unless the color and material of the screen are considered.
It is general that the distance of projection between the projection type image display device and the screen is variable. The amount of projected light per unit area on the screen will be varied depending on the distance of projection. Even if the ambient light is invariable, the image appearance will be varied depending on the amount of projected light per unit area.
Even when the conventional system for selecting and applying the regulating values is taken, therefore, the image display device cannot properly regulate the image appearance unless the distance of projection is also considered.
Particularly, when the image display device is to correct both the brightness and color of an image, a huge amount of data relating to regulating values to be previously stored will be required even though a system is taken which is designed to determine a regulating value based on the color and material of the screen as well as the distance of projection in addition to the illuminating light. The previous setting of regulating values is not practical.
Rather than the screen, a wall may be used as the plane of projection. In this case, it is extremely difficult to previously provide regulating values for every wall having different colors and materials.
Since an image projected by the image display device is usually observed by a plurality of observers, the calibration must be carried out so that no unpleasantness will be given to the observers.
For example, when a presentation is to be made by projecting an image through the conventional projector, the projector performs the calibration prior to the presentation, but not during the presentation.
However, the influence of the ambient light may be varied during the presentation, that is, during display of the image. For example, the image appearance will be varied when the external light changes.
In this case, the observers will be kept waiting as the calibration of the projector is being carried out after interruption of the presentation. If the calibration of the projector is to be performed in consideration of the influence of ambient light, both the color and brightness must be calibrated. If the calibration relating to both the color and brightness is made each time when the ambient light changes, the observers will be kept waiting for a further time period.